<html>
<head>
	<meta charset="UTF-8">
	<meta content="IE=edge" http-equiv="X-UA-Compatible">
	<meta content="initial-scale=1.0, maximum-scale=1.0, user-scalable=no, width=device-width" name="viewport">
	<title>2922：[Poi1998]Chase</title>
	<!-- css -->
	<link href="../css/base.min.css" rel="stylesheet">
	<link href="../css/project.min.css" rel="stylesheet">
	
	<!-- favicon -->
	<!-- ... -->
</head>
<body class="page-brand">
	<header class="header header-transparent header-waterfall ui-header">
		<ul class="nav nav-list pull-left">
			<li>
				<a data-toggle="menu" href="#menu">
					<span class="icon icon-lg">menu</span>
				</a>
			</li>
		</ul>
		<a class="header-logo header-affix-hide margin-left-no margin-right-no" data-offset-top="213" data-spy="affix">[Poi1998]Chase</a>
		<span class="header-logo header-affix margin-left-no margin-right-no" data-offset-top="213" data-spy="affix">[Poi1998]Chase</span>
	</header>
	<nav aria-hidden="true" class="menu" id="menu" tabindex="-1">
		<div class="menu-scroll">
			<div class="menu-content">
				<a class="menu-logo" href="../index.html">BZOJ离线题库</a>
				<ul class="nav">
					<li>
						<a class="waves-attach" data-toggle="collapse" href="#problems">题目</a>
						<ul class="menu-collapse collapse in" id="problems">
							<li>
								<a class="waves-attach" href="../index.html">主页</a>
							</li>
							<li>
								<a class="waves-attach" href="../list.html">题目列表</a>
							</li>
						</ul>
					</li>
					<li>
						<a class="collapsed waves-attach" data-toggle="collapse" href="#about">关于</a>
						<ul class="menu-collapse collapse" id="about">
							<li>
								<a class="waves-attach" href="../about.html">关于此项目</a>
							</li>
						</ul>
					</li>
					
				</ul>
			</div>
		</div>
	</nav>
	<main class="content">
		<div class="content-header ui-content-header">
			<div class="container">
				<h1 class="content-heading">
                [Poi1998]Chase                </h1>
                <p>时间限制：1s&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;  空间限制：128MB</p>			</div>
		</div>
		<div class="container">
			<section class="content-inner margin-top-no">
				<div class="row">
					<div class="col-lg-13 col-md-13">
						<div class="card margin-bottom-no">
							<div class="card-main">
								<div class="card-inner">
									
                                <h3>题目描述</h3><p><p><span style="font-size: medium"><br />
追逐游戏是一个双人游戏，假设有玩家A和B。一个棋盘包含由1到n编号的格子。对于一对编号不同的格子，会给定它们之间是否相连。每个玩家控制一个棋子。开始的时候，每个玩家的棋子会放在某个特定的不同的格子。在一回合中，玩家可以移开它的棋子，移到一个相邻的格子。</span></p>
<p><span style="font-size: medium">一个棋盘有下面属性：</span></p>
<p><span style="font-size: medium">* 不存在三角形连接的格子<br />
* 每个格子都可以被走到</span></p>
<p><span style="font-size: medium">一次游戏由若干回合组成。在每个回合，每个玩家只能动一步。每回合A先开始动。</span></p>
<p><span style="font-size: medium">当两个棋子站在一起的时候，我们说A被B吃掉了。给定棋子的初始位置，假定AB都选用最佳决策，判断B是否必胜。如果是的话，需要多少回合。</span></p>
<p><span style="font-size: medium">例如：</span></p>
<p><span style="font-size: medium">&lt;img src=&quot;</span><a href="http://main.edu.pl/en/images/OI5/gon.gif"><span style="font-size: medium">http://main.edu.pl/en/images/OI5/gon.gif</span></a><span style="font-size: medium">&quot; alt=&quot;example&quot; /&gt;</span></p>
<p><span style="font-size: medium">上图的棋盘，用边连起来的是相邻的格子。如果开始的时候，A和B的棋子分别站在9和4的位置，那么在第3轮B可以吃掉A。如果A和B分别在8和4，那么B就无法吃掉A。</span></p>
<p></p></p><hr/><h3>输入格式</h3><p><p><span style="font-size: medium">第一行，4个整数：格子数量n(2&lt;=n&lt;=3000)，边数m(n-1&lt;=m&lt;=15000)，A和B的初始位置a b(a &lt; b)<br />
下面m行：(u, v) 描述一对相邻的格子</span></p>
<p></p></p><hr/><h3>输出格式</h3><p><p><span style="font-size: medium">如果B能吃掉A的话，输出最少需要的回合数。否则输出&quot;NIE&quot;</span></p>
<p></p></p><hr/><h3>样例输入</h3><pre>9 11 9 4
1 2
3 2
1 4
4 7
7 5
5 1
6 9
8 5
9 8
5 3
4 8

</pre><hr/><h3>样例输出</h3><pre>
3
</pre><hr/><h3>提示</h3><p>没有写明提示</p><hr/><h3>题目来源</h3><p>没有写明来源</p>
								</div>
							</div>
						</div>
					</div>
				</div>
				
				
			</section>
		</div>
	</main>

	<div class="fbtn-container">
		<div class="fbtn-inner">
			<a class="fbtn fbtn-lg fbtn-brand-accent waves-attach waves-circle waves-light waves-effect" data-toggle="dropdown" aria-expanded="true"><span class="fbtn-text fbtn-text-left">Menu</span><span class="fbtn-ori icon">apps</span><span class="fbtn-sub icon">close</span></a>
			<div class="fbtn-dropup">
				<a class="fbtn fbtn-brand waves-attach waves-circle waves-light waves-effect" href="../list.html" target="_self"><span class="fbtn-text fbtn-text-left">题目列表</span><span class="icon">menu</span></a>
				<a class="fbtn fbtn-green waves-attach waves-circle waves-effect" href="../index.html" target="_self"><span class="fbtn-text fbtn-text-left">返回主页</span><span class="icon">home</span></a>
				<a class="fbtn waves-attach waves-circle waves-effect" href="http://www.lydsy.com/JudgeOnline/submitpage.php?id=2922" target="_blank"><span class="fbtn-text fbtn-text-left">提交代码</span><span class="icon">send</span></a>
				<a class="fbtn fbtn-orange waves-attach waves-circle waves-effect" href="http://www.lydsy.com/JudgeOnline/wttl/wttl.php?pid=2922" target="_blank"><span class="fbtn-text fbtn-text-left">试题讨论</span><span class="icon">chat</span></a>
				
			</div>
		</div>
	</div>

	<!-- js -->
	<script src="../js/jquery.min.js"></script>
	<script src="../js/base.min.js"></script>
	<script src="../js/project.min.js"></script>
</body>
</html>